!(function (window) {
  /* 设计图文档宽度 */
  var docWidth = 750;
  var doc = window.document,
  docEl = doc.documentElement,
  resizeEvt ="orientationchange" in window ? "orientationchange" : "resize";
  var recalc = (function refreshRem() {
  var clientWidth = docEl.getBoundingClientRect().width;
  /* 8.55：小于320px不再缩小，11.2：大于420px不再放大 */
  docEl.style.fontSize =Math.max(Math.min(20 * (clientWidth / docWidth), 11.2), 8.55) * 5 +"px";
    return refreshRem;
  })();
  /* 添加倍屏标识，安卓为1 */
  docEl.setAttribute("data-dpr",window.navigator.appVersion.match(/iphone/gi)? window.devicePixelRatio: 1);
  if (/iP(hone|od|ad)/.test(window.navigator.userAgent)) {
    /* 添加IOS标识 */
    doc.documentElement.classList.add("ios");
    /* IOS8以上给html添加hairline样式，以便特殊处理 */
    if (parseInt(window.navigator.appVersion.match(/OS (\d+)_(\d+)_?(\d+)?/)[1],10) >= 8){
      doc.documentElement.classList.add("hairline");
    }
  }
    if (!doc.addEventListener) return;
    window.addEventListener(resizeEvt, recalc, false);
    doc.addEventListener("DOMContentLoaded", recalc, false);
  })(window);